DE60220343T2 - Welding device with a miniaturized laser beam - Google Patents

Description

This invention relates to a high-power laser beam welding apparatus having a power of, for example, 500 watts to several kilowatts, which is miniaturized according to the preamble of claim 1, and which is capable of being brought very close to welding surfaces of workpieces and welding To reach surfaces that are difficult to reach due to obstacles located above them. In Scripture EP 300458 A Such a device is described.

It is known to metals by means of a high-power laser beam welding. For this one uses a welding device, usually one elongated has formed closed space inside which the laser beam can circulate and exit at one end of the enclosed space can to hit the workpiece to be welded. The enclosed space is light-tight to protect the operator from any unwanted propagation of the laser beam outside the completed Space to protect. The term "light-tight" means that the closed space any unwanted leakage of the laser beam, for example, due to the adjustment of an optical component, prevented.

Of the Laser beam tracks one inside the enclosed space Path on which are in succession: a high-power laser light source, a convergent optical system and a so-called "front opening" through which the laser beam from the enclosed space in the direction of the workpiece to be welded again can escape. The convergent optical system focuses the laser beam onto one Focus that is outside of the enclosed space is, of course, the workpiece is brought to this focal point to be welded. The laser light source may be a laser light generator or the end of an optical fiber, the laser beam from a remote laser light generator in the closed space leads, be. In more complicated embodiments the enclosed space can be articulated and / or one or Several optical mirrors included in the path of the laser beam are arranged and the appropriate deflections of the laser beam guarantee.

to Simplification of the idiom is said below An object is located in front of the front opening when it opens except for Device and opposite the front opening located. Conversely, one says below that an object behind the front opening when it is on the other side of the front opening.

• – Verkleinerung des Durchmessers der Frontseitenöffnung auf das absolute Minimum, um die Laserstrahlen noch durchzulassen,
• – Einspritzen eines neutralen Gases unter ausreichendem Druck in den abgeschlossenen Raum, woraufhin das Gas durch die Frontseitenöffnung entweicht und so ein Hindernis für die Dämpfe und Spritzer des schmelzenden Metalls bildet; das Gas kann auch, wie in der Schrift EP 300458 A beschrieben, in die Frontseitenöffnung und zu dem Zwischenraum zwischen dem Spiegel und dem Schweißbereich hin gespritzt werden,
• – Entfernen der Optik-Komponenten von der Frontseitenöffnung oder Entfernen der Frontseitenöffnung von dem zu schweißenden Werkstück.

The optics components must be protected from the fumes and splashes of the melting metal during welding. Normally, the enclosed space provides this protection function, however, fumes and splashes of the melting metal can pass through the front opening, penetrate the enclosed space, and stain the optical components, particularly those located near the front opening. Different means are used to prevent this:

• Reduction of the diameter of the front opening to the absolute minimum in order to let the laser beams through,
• Injecting a neutral gas under sufficient pressure into the enclosed space, whereupon the gas escapes through the front-side opening and thus forms an obstacle to the vapors and splashes of the melting metal; the gas can also, as in the Scriptures EP 300458 A sprayed into the front opening and to the gap between the mirror and the welding area,
• Removing the optical components from the front opening or removing the front opening from the workpiece to be welded.

• – sich dieser Spiegel sehr nahe an dem schmelzenden Metall im Schweißbereich befindet,
• – der Druck des schützenden Gases aus wirtschaftlichen Gründen, und um das schmelzende Metall nicht zu verstreuen, notwendigerweise begrenzt bleibt; in der Figur ist zu sehen, dass die Öffnung deutlich größer ist als der Laserstrahl, der durch sie gelangt; dies ermöglicht es, den Schweißbereich mit neutralem Gas zu umgeben, ohne einen Gasstrom zu erzeugen, der das im Schmelzen befindliche Metall zerstreut; dafür hat das schützende Gas nur eine geringe Geschwindigkeit, wenn es die Frontseitenöffnung durchquert; es kann daher nur ein schwaches Hindernis gegen die Dämpfe und Spritzer von schmelzendem Metall bilden, und der Spiegel wird daher schnell beeinträchtigt.

In the patent EP 0 514 235 there is described an apparatus capable of welding surfaces over which obstacles are located, this welding apparatus comprising a tubular elongated closed space with a laser light source disposed at one end, the front opening being laterally disposed at the other end Mirror is disposed behind the front opening and deflects the coming of the laser light source laser beam toward this, with the working end of the welding device between the surfaces to be welded and the obstacles is inserted, in this case, the inner wall of a pipe of a nuclear power plant. A neutral gas escapes through the front opening, thereby protecting the surface in the welding process from the ambient air. However, this welding device has the disadvantage that the mirror is exposed to the fumes and splashes of molten metal because:

• This mirror is very close to the melting metal in the weld area,
• - the pressure of the protective gas for economic reasons, and not to disperse the melting metal, necessarily remains limited; in the figure it can be seen that the opening is significantly larger than the laser beam that passes through it; this makes it possible to surround the welding area with neutral gas without generating a gas stream which dissipates the metal to be melted; but the protective gas has only a low Geschwin when passing through the front opening; therefore, it can only form a weak obstacle against the fumes and splashes of melting metal, and therefore the mirror is quickly deteriorated.

This Therefore, mirrors often have to be replaced. This is one Welding device though for repairs thinner workpieces suitable for only a small amount of power is required, but not for a commercial one Use in the workshop on thick workpieces with high laser power.

One first to be solved Problem is to propose a welding head, whose Front opening be brought very close to the surface to be welded can, without the optics components by the steam and splashes of Melting metal can be stained and without this melting Metal is swirled, for example, by an emerging from the front opening Gas flow.

One second to be solved Problem is to propose a welding head, which between the to be welded surfaces and that about this located, nearby obstacles can be inserted.

to solution of the first problem is miniaturized with this invention Laser beam welding apparatus according to claim 1 proposed.

• a) drückt der Primärstrom die Dämpfe und Spritzer von schmelzendem Metall, die auf die Frontseitenöffnung gerichtet sind, zurück, wodurch verhindert wird, dass diese Dampfe und Spritzer ins Innere des Schweißkopfs eindringen;
• b) trifft der Nebenstrom auf den Primärstrom, und zwar im rechten Winkel zu diesem und in dem Augenblick, in dem er durch die Frontseitenöffnung austritt, was zur Wirkung hat, dass der Primärstrom abgelenkt wird und so daran gehindert wird, auf das flüssige Metall zu treffen, das sich ein Stückchen weiter im Bereich des Brennpunkts bildet;

The term "transverse" is understood to mean that the secondary flow is guided parallel to the face of the front opening

• a) the primary flow returns the fumes and splashes of molten metal directed at the front opening, preventing these fumes and spatter from entering the interior of the weld head;
• b) the secondary flow impinges on the primary flow, at right angles to it and at the moment it exits through the front-side opening, which has the effect of deflecting the primary flow and thus preventing it from reaching the liquid metal meet, which forms a little further in the area of the focal point;

So can the vapors and splashes of melting metal not through the front opening in the welding head penetrate and the melting metal sweat is through the primary gas flow not swirled, deformed or even scattered so that it becomes possible the welding head very much close to the welding surface to bring, and in this way the first problem is solved.

Of the Operator provides the primary current with a sufficient force to melt the fumes and splashes Metal facing the front opening approach, continued to press. Likewise, the operator provides the bypass with sufficient force one to the primary stream to distract him so that he is the liquid Metal that forms near the focal point in front of the front opening, not reached, at least not directly.

advantageously, the welding head is further away a shield disposed in front of the front opening, wherein This shield made of rigid, high temperature resistant material consists of, for example, Nobelium, this shield is interspersed by a hole on the geometry axis of the Front opening located. This shield allows the primary current and to guide the sidestream transversely to the front opening, ensuring the protection of the melting Metal in front of the primary stream improved.

Of the Shield also forms a mechanical barrier to the vapor and splashes of melting metal, which affect the welding head and around the front opening move around, which reduces the encrustation of the welding head. In particular, the shield forms an obstacle to the vapors and Splashes of melting metal extending between the front opening and the nozzle move, taking these splashes without the shield by the side stream in front of the front opening promoted could become. Thus, despite the hole between the melting metal and the Front opening by this obstacle effect before the integrity of the interior of the welding head the vapors and splashes of melting metal further improved.

advantageously, the shield is removable to be cleaned or replaced become when it is encrusted.

Also advantageously, the welding head has a shell surrounding the front opening, the nozzle and the shield, the shell being open and expanding in front of the shield, the shell being made of a thin, pliable and gas tight material, with a gap between is provided at least one edge of the shield and the jacket. In this way, the jacket cooperates with this gap to return the gas of the primary flow and the secondary flow above the area currently in the welding process, whereby the welding area with lower gas consumption can be protected from the ambient air. By having the sheath of an appropriate length to come into contact with the workpiece surface to be welded This sheath also retains the gas of the primary and secondary streams above the weld area, thereby reducing gas consumption and oxidation of the workpiece during welding.

Also Advantageously, the welding head further comprises a mirror on, which is located directly behind the front opening and the Laser beam deflects towards this front opening. Through this Arrangement, the space requirement of the welding head behind the front opening can be reduced which makes it possible will, the welding head between the ones to be welded surfaces and to push a nearby obstacle, with this arrangement solved the second problem can be.

Especially Applicant claims a welding head whose thickness E1 is between the front opening and that of the front opening opposite Wall is less than 50 mm.

The Invention is getting closer from a detailed description of an embodiment and the attached figures out.

1 shows a welding head, which is attached to the end of a welding device, which is supplied by an optical fiber with light.

2 represents the actual welding head in detail.

It is going on first 1 Referenced. The welding device 10 has a welding head 12 up, from a wall 14 is formed, which has a cavity 16 surrounds the wall 14 is light-tight, with the wall 14 however a so-called "inlet opening" 18 and a so-called "front opening" 20 having a laser beam 22 is able through the inlet opening 18 in the cavity 16 penetrate and out of this cavity 16 through the front opening 20 retreat by making an optical path 24 tracked. The welding head 12 also has a supply 26 which can be connected to a source of neutral, pressurized gas, such as argon, with this supply 26 in this example, a line is through the wall 14 runs and into the cavity 16 empties.

In this example, the inlet port 18 and the front opening 20 flat, circular and on the optical path 24 centered, which forms their geometry axes. The inlet opening 18 and the front opening 20 are at right angles to each other. A mirror 28 is in the cavity 16 on the optical path 24 arranged. The mirror 28 deflects the laser beam 90 ° to the front opening 20 to lead. Of course, the mirror needs 28 withstand high temperatures. For example, it may be ZnSe, copper with a cooling circuit or "dielectric".

The welding device 10 also has a generally elongated shaped enclosed space 30 on, its opposite ends with the reference numbers 30a and 30b are designated. A laser light source 32 is at a first end 30a arranged and produces the laser beam 22 , the interior of the closed room 30 traverses by the optical path 24 follows, with the laser beam 22 at the other end 30b arrives at which the welding head 12 is attached, the end 30b the inlet opening 18 surrounds, with the laser beam 22 in this way from the inside of the closed space 30 in the cavity 16 of the welding head 12 can get.

In this example, the laser light source 32 punctiform and is formed by an optical fiber, the laser light from a remote, not shown generator with its end 32a inside the locked room 30 leads. In this example, the end also becomes 30a of the closed room 30 from a foot part 34 formed, which is the laser light source 32 holds, with this foot part 34 to the other end 30b from a straight pipe 36 is continued, with the straight tube 36 attached to the foot part by screws without reference numbers. The welding head 12 is also at the end of the straight pipe 36 appropriate. In a preferred embodiment, the connection is between the welding head 12 and the closed room 30 removable, so that welding heads 12 with different geometries with straight tubes 36 of different lengths can be combined.

The welding device 10 contains on the optical path 24 an optics system 42 that the laser beam 22 to a focal point 44 in front of the front opening 20 outside the welding head 12 bundles, with this focus 44 on the optical path 24 located. If the laser light source 32 is punctual, is the optics system 42 convergent and results at this focal point 44 a real image from the laser source 32 , Furthermore, the convergent optical system includes 42 two convergent lenses. The first lens, a so-called collimator lens 46 Forms the diverging laser beam coming out of the end 32a the optical fiber comes in a parallel beam, wherein the second lens 48 , a so-called focusing lens, this parallel beam in one on the focal point 44 transforming convergent light beam. This arrangement allows straight tubes 36 of different lengths without changing the position of the focus 44 opposite the front opening 20 and the welding head 12 changes as long as the relative position of the collimator lens to the end 32a the laser light source and the relative position of the focusing lens 48 to the welding head 12 remain unchanged. In this example, the optical system includes 42 also a prism 49 that between the collimator lens 46 and the focusing lens 48 is arranged close to the latter, the prism 49 the laser beam 22 in its cylindrical section cuts across half of its cross section, the prism 49 half of the laser beam 22 easily deflects to a second focus, which has no reference and to the focal point 44 is slightly offset, this arrangement is known per se.

The welding head will now be described in more detail and it will open simultaneously 1 and 2 Referenced.

The supply 26 produces a gas stream 50 , the so-called "primary stream." The welding head 12 is above the surfaces 52a the workpieces to be welded 52 positioned, with the focus 44 on these surfaces 52a is located, with the welding head 12 a shift parallel to the surfaces 52a subjected to this shift by the velocity vector 54 is shown. Under the heat of the laser beam 22 The metal liquefies near the focal point 44 and then gets stuck again to the weld 58 to build. With the reference number 56 is called the liquid metal, which is during welding near the focal point 44 forms. This liquid metal releases vapor and splatters through the front opening 20 get into the locked room 16 of the welding head 12 penetrate and in contact with the mirror 28 that can come right behind the front opening 20 located. When you look at the strength of the primary stream 50 Increased to prevent the fumes and splashes of melting metal 56 in the locked room 16 penetrate, then the primary current hits 50 of course with too much speed on the liquid metal 56 What causes its deformation so even its scattering and so the just forming weld 58 deformed.

The welding head 12 has a nozzle 60 which can be connected to a compressed gas source, not shown, wherein said nozzle is positioned so that it has a so-called secondary compressed gas flow 62 that gives off in front of the front opening 20 and flows across this. The secondary gas flow 62 sweeps the entire surface of the front opening 20 but without this front opening 20 inside the locked room 16 penetrate. The secondary gas flow 62 therefore comes in front of the front opening 20 with the primary gas stream 50 essentially at right angles to the optical path 24 in collision, where the secondary gas flow 62 the primary gas stream 50 deflected in this way, so that it no longer directly on the liquid metal 56 meet and cause its dissipation. By the term "front wall" 64 becomes the outer surface of the wall 14 of the welding head 12 referred to, which is around the front opening 20 is around. The front wall 64 is practically flat and is at right angles to the optical path 24 where he passes through the front opening 20 runs. The nozzle 60 is on the front wall 64 attached, but to the front opening 20 arranged off-center. The nozzle 60 but is to the front opening 20 directed and generates the secondary gas stream 62 across the front opening 20 and parallel to the front wall 64 ,

• – Erstens kanalisiert er den Nebengasstrom 62 und den Primärgasstrom 50 parallel zur Frontseitenwandung 64, wodurch der Schutz des flüssigen Metalls 56 vor dem Primärgasstrom 50 verbessert wird.
• – Zweitens bildet er ein Hindernis gegen die Dämpfe und Spritzer des schmelzenden Metalls 56, wodurch die Verkrustung des Schweißkopfs 12 selbst vermieden werden kann.
• – Drittens bildet er ein Hindernis gegen die Dämpfe und Spritzer des schmelzenden Metalls, die sonst zwischen die Frontseitenöffnung 20 und die Düse 60 gelangen und dann durch den Nebengasstrom 62 zur Frontseitenöffnung 20 hin umgelenkt würden. So wird durch diese zusätzliche Hinderniswirkung trotz des Lochs, das sich auf dem optischen Weg befindet, der Schutz der Optik-Komponenten, insbesondere des Spiegels 28, vor den Dämpfen und Spritzern von schmelzendem Metall 56 durch den Schutzschild 66 noch weiter verbessert.

Further, in front of the front opening 20 a flat, thin shield 66 parallel to the front wall 64 and thus at right angles to the optical path 24 arranged, with the nozzle 60 yourself between the front wall 64 and the shield 66 is located, passing through the shield 66 a hole 68 is drilled on the optical path 24 centered, taking off the shield 66 closer to the front wall 64 is the focal point 44 , This shield is made of a heat-resistant material, such as Nobelium. Such a shield offers several advantages:

• - First, it channels the secondary gas flow 62 and the primary gas stream 50 parallel to the front wall 64 , thereby protecting the liquid metal 56 before the primary gas flow 50 is improved.
• - Second, it forms an obstacle against the fumes and splashes of the melting metal 56 , whereby the encrustation of the welding head 12 even be avoided.
• - Third, it forms a barrier against the fumes and splashes of melting metal that would otherwise be between the front opening 20 and the nozzle 60 arrive and then through the secondary gas flow 62 to the front opening 20 would be redirected. Thus, despite the hole located on the optical path, this additional obstacle effect protects the optical components, in particular the mirror 28 , before the fumes and splashes of melting metal 56 through the shield 66 even further improved.

This shield can be made of Nobelium, of a metal alloy whose main constituent is Nobelium, or of a nickel-base superalloy. The hole 68 and the front opening 20 are in relation to the focal point 44 preferably arranged the same, so that their dimen to the absolutely necessary for the passage of the laser beam 22 can be limited.

Further, a coat 70 provided the laser beam 22 between the front opening 20 and the focal point 44 surrounds, with one end of the shell up to the front wall 64 goes up and forms an opening that the front opening 20 surrounds, while the other end of the mantle has a widening opening around the focal point 44 forms around, with this coat 70 made of a heat-resistant, especially against splashes of liquid metal 56 durable material, said jacket is gas-tight side, said jacket also the nozzle 60 and the protective shield 66 surrounds, leaving a gap 74 to the nozzle 60 opposite edge 66a of the protective shield 66 stays down. The jacket has a suitable height, so that its widening end 70a during welding with the surface 52a of the workpiece to be welded 52 flees. The coat 70 guides and holds the primary and secondary streams 50 . 62 above the liquid metal 56 by passing them through the space defined above 74 to flow. The gas thus guided protects the surface to be welded 52a around the liquid metal 56 around effectively. This gas then flows between the jacket 70 and the surfaces to be welded 52a ,

During welding, the welding head preferably becomes in the direction of the nozzle 60 exiting secondary flow 62 postponed. In this way, the combined primary and secondary streams come 50 . 62 at a reduced speed parallel to the currently forming weld 58 which prevents it from becoming deformed.

In In practice, the shield is removable to be cleaned or replaced when he gets through the fumes and splashes of liquid Metal is too heavily encrusted. Is the welding head highly miniaturized, then it can be held by two screws in the front side wall be screwed with the nozzle between the shield and the front side wall is sandwiched.

Of the Coat is cut out of a tightly woven fiberglass fabric, wherein this jacket is coated on its outside with a silicone elastomer layer is that is high temperature resistant, these materials are commercially available. Such a coat is flexible and tear-resistant at the same time. In addition, guaranteed the silicone elastomer the gas tightness of the jacket, and the glass fiber fabric protects that Silicone elastomer before the fumes and splashes of melting metal and heat radiation.

The invention has made it possible to greatly miniaturize the welding device. Therefore, the applicant further claims a welding apparatus with a welding head according to this invention, whose thickness E1, along the geometry axis 24a the front opening does not exceed 50 mm. In the case of a welding head 12 with coat 70 In practice, this space requirement corresponds to the distance between the widening opening 70a of the coat 70 and the outside 76 the wall 14 behind the front opening 20 , This allows the welding device 10 , Surfaces 52a of workpieces 52 to weld, though an obstacle 78 at a distance E1 above the surfaces to be welded 52a located.

In particular, this invention has made it possible to carry out a welding head powered by a 4kW YAG laser while still leaving only a clearance of 24mm above the surfaces to be welded 52a requires.

Claims (10)

Miniaturized laser beam welding device ( 10 ), which has a welding head ( 12 ) contained by a wall ( 14 ) is formed, which has a cavity ( 16 ), whereby the wall ( 14 ) a first opening, a so-called "inlet opening" ( 18 ) and a second opening, a so-called "front opening" ( 20 ), wherein a laser beam ( 22 ) is able to pass through the inlet opening ( 18 ) in the welding head ( 12 ) and through the front opening ( 20 ) to exit from this by a predetermined optical path ( 24 ), wherein the welding head ( 12 ) a supply ( 26 ) with compressed gas capable of being in the cavity ( 16 ) a so-called "primary gas stream" ( 50 ) to be generated from the welding head ( 12 ) through the front opening ( 20 ), and a nozzle ( 60 ), which can be connected to a compressed gas source, said nozzle ( 60 ) outside the welding head ( 12 ) on the wall ( 14 ), wherein the nozzle ( 60 ) generates a so-called secondary compressed gas flow, the free space immediately in front of the front side opening ( 20 ) transversely spread, characterized in that the welding head ( 12 ) a protective shield ( 66 ) located in front of the front opening ( 20 ), the protective shield ( 66 ) substantially flat and parallel to the front opening ( 20 ) surrounding wall ( 14 ), the front wall ( 64 ), this protective shield ( 66 ) is penetrated by a hole located in front of the front opening ( 20 ), wherein the nozzle ( 60 ) between the protective shield ( 66 ) and the front wall ( 64 ) is arranged. Device according to claim 1, characterized in that that the protective shield is removable. Device according to Claim 1 or 2, characterized that the shield is made of Nobelium. Device according to claim 3, characterized in that the welding head ( 12 ) a coat ( 70 ) having the front side opening ( 20 ), the nozzle ( 60 ) and the protective shield ( 66 ), the shell ( 70 ) in front of the protective shield ( 66 ) is open and is and widens, wherein the jacket consists of a thin, flexible and gas-tight material, with a gap ( 74 ) between at least one edge ( 66a ) of the protective shield ( 66 ) and the coat ( 70 ) is provided. Device according to one of claims 1 to 4, characterized in that the welding head ( 12 ) also a mirror ( 28 ) directly behind the front opening ( 20 ), wherein the mirror ( 28 ) from the inlet opening ( 18 ) coming laser beam ( 22 ) to the front opening ( 20 ) deflects. Device according to claim 5, wherein the wall ( 14 ) a part ( 76 ) behind the front opening ( 20 ), characterized in that the welding head ( 12 ) has a thickness E1 which is at most 50 mm, the thickness E1 between the front opening ( 20 ) and the part ( 76 ) of the wall ( 14 ) behind the front opening ( 20 ) is measured. Device according to claim 5 or 6, characterized in that it comprises a generally oblong shaped enclosed space ( 30 ) whose ends are denoted by the reference numbers ( 30a ) and ( 30b ), wherein at a first end ( 30a ) a laser light source ( 32 ), the other end ( 30b ) on the welding head ( 12 ) and the inlet opening ( 18 ) surrounds. Apparatus according to claim 7, characterized in that the laser light source ( 32 ) is punctual and that it is an optical system ( 42 ) received from the laser source ( 32 ) a real image at a focal point ( 44 ) in front of the front opening ( 20 ). Apparatus according to claim 8, characterized in that the laser light source ( 32 ) is an optical fiber. Apparatus according to claim 7 or 8, characterized in that the connection between the welding head ( 12 ) and the enclosed space ( 30 ) is removable.